JPH0210411A - Actuator controller - Google Patents

Abstract

PURPOSE:To improve the control performance by collectively calculating all disturbance torque to be suppressed in the control system of an actuator and feeding back it. CONSTITUTION:A motor 1 and a load 2 like a machine tool driven by this motor 1 are provided, and an angular acceleration omegas and an angular velocity omegaare measured, and an observer (feedback means) 3 is used to obtain disturbance torque Tdis. This disturbance torque Tdis is expressed with a variation term of load torque, a term of friction torque varied by the force of inertia generated by the variance of the moment of inertia, the force of viscosity, and the Coulomb's force, and a term of torque ripple due to the variance of the torque constant. Consequently, they are used to collectively calculate all disturbance torque to be suppressed by the control system of the motor 1, and this calculation is not affected at all though values of respective terms are functions of time. This obtained disturbance torque Tdis is fed back.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an actuator control device that controls force or torque of various actuators.

[Prior Art] As this type of control device, a servo motor control device having a control block as shown in FIG. 11 is well known. This control device operates in a linear range in which a limiter inserted to prevent overcurrent and overspeed does not operate, and a proportional-sufficient-integral element (PI control) is used as a compensation element. In the figure, θ is the rotation angle of the servo motor.
θ″″ is the rotation angle command value, ω is the angular velocity of the servo motor, ω
r@T is the angular velocity command value, J is the moment of inertia around the rotation axis, and T ext is the load torque, and the rotation angle θ and angular velocity ω are detected and fed back. Design guidelines for such control systems place emphasis on optimizing response to set values.

This situation also applies to other actuators.

[Problems to be Solved by the Invention] According to modern control theory, in order to optimize a system, it is necessary to know all the state variables of the system.

On this point, in the case of the control device shown in Fig. 11 mentioned above, although the values of position and velocity can be known through sensors, the control is performed without knowing the values of angular acceleration and load torque 1.6. . If these values are known, better control becomes possible. This also applies to the control of other actuators, as well as rotational movement,
The same thing can be said regardless of linear motion.

An object of the present invention is to provide a novel control device that takes even the acceleration level into consideration.

[Means for Solving the Problems] The actuator control device of the present invention combines an actuator with a force constant or torque constant Kt and a load that applies a load force or load torque of T ext to the actuator, and The inertia force or moment of inertia converted around the rotational axis is J, the viscous friction force calculated based on the center of gravity position, or the viscous friction torque converted around the rotational axis is Dω, and the Coulomb friction force or In an actuator control device that controls the output of the Moeki actuator according to the control fla of the actuator, when the Coulomb friction torque converted around the rotation axis is F, the speed component ω or the acceleration component ωs of the actuator
From, the disturbance force or disturbance torque l11 given by the following equation
4. An actuator control device comprising feedback means for determining 4° and feeding back compensation control (U) corresponding to this to the actuator.

Td,, 1-(Text Textn) + (J
J n) S (c) + (D-Dn) ω + (P-Fn
) + (Kshi.-Kt)Ia However, Text. is the nominal value of load force or load torque 1, ■o
is the nominal value of the inertia force or the moment of inertia when converted to the center of gravity position, D is the viscosity coefficient when the center of gravity position is replaced, or the viscosity coefficient when converted around the rotation axis, Dn is the viscosity coefficient when the center of gravity position is replaced, or The nominal value of the viscosity coefficient when converted around the rotation axis, Fo is the nominal value of the Coulomb friction force when converted to the center of gravity or the Coulomb friction force when converted around the rotation axis, Ktn is the nominal value of the force constant or torque constant of the actuator, S is the Laplace operator.

"Operation" The actuator control device of the present invention collectively calculates and feeds back all the disturbance forces or disturbance torques that should be suppressed in the actuator control system, so that the actuator parameter values are not fluctuated and the nominal values are maintained. By fixing the torque constant or torque constant to a model with a nominal moment of inertia, we aim to significantly improve control performance.

[Example] Hereinafter, an example of the present invention will be described based on FIGS. 1 to 1O.

1 to 7 show a first embodiment of the present invention.

First, disturbance torque will be explained.

The amplifier that supplies power to the electric motor (actuator) 1 can be thought of as a controlled current source using FETs, high-speed transistors, PWM (pulse width modulation) technology, etc. The model of the load 2, such as a robot manipulator or a robot manipulator, can be simplified as shown in FIG. Here, 1 arot is the control current command value, Ia is the control current, Kt is the torque constant of motor 1, J is the moment of inertia around the rotation axis, D is the viscosity coefficient of the mechanical system around the rotation axis, and F is the rotation axis around the rotation axis. Coulomb friction force, T ext is load torque, S is Laplace operator,
ω is the angular velocity, and the total torque of the load 2 applied to the motor l is Text+F+(JS+D)ω.

The constants and coefficients in the above formula each have time dependence. Fluctuations in the moment of inertia J pose a major problem in machine tools, robot manipulators, etc., and the frictional force F also varies significantly depending on temperature, speed, force, etc., which also poses a problem.

Therefore, the angular acceleration ωs and the angular velocity ω are measured, and the disturbance torque T dr a is determined using an observer (feedback means) 3 as shown in FIG. The subscript n in the figure means a nominal value, and Kt, is the nominal value of the torque constant of the electric motor I, T.

,. is the nominal value of the load torque, Fn is the nominal value of the Coulomb friction force around the rotation axis, and Dn is the nominal value of the viscosity coefficient of the mechanical system around the rotation axis. As a result, the disturbance torque T dig
is determined by the following formula (1).

T , , , = (Text Textn) + (J
J n) Sω+(I)-Do)ω+(F'-1
? ' n) + (K tn K t ) I a"'
...(1) In the above equation, the first term on the right side is the load torque fluctuation term, the second term is the inertia force generated by the fluctuation of the moment of inertia, and the third and fourth terms are the viscous force and Coulomb force. The fifth term represents torque ripples caused by fluctuations in the torque constant (for example, torque ripples caused by spatial harmonics of magnetic flux). If you want to use a formula like this, you can use an electric motor!
The control system allows all disturbance torques to be suppressed to be calculated at once, but even if the value of each term is a function of time, it is not affected at all.

Then, the disturbance torque 'I dis
is fed back as shown in Figure 1. The feedback can be equivalently transformed as shown in FIGS. 4 and 5. These block diagrams indicate a nominal torque constant Kt, a nominal moment of inertia Jn, and a nominal viscosity coefficient Dn, regardless of variations in the parameters of the electric motor l.
The control stiffness is fixed to the model with
This means that, in theory, it can be determined arbitrarily. In other words, the electric motor 1 and the load 2 coupled thereto can be seen as a system without load changes, inertia changes, friction changes, and torque ripple fluctuations.

FIG. 6 and FIG. 7 are diagrams for explaining an experimental example of torque control using the control device of the present invention.

This experimental device applies a torque command T cmd to a manipulator (load) 2, and a reaction force '
The detection signal of i'rsac+ is filtered and fed back, and the angular velocity ω of the manipulator 2 is given to the above-mentioned observer 3 to calculate the disturbance torque Talm.
It is designed to provide feedback. therefore,
An observer 3 is used in the inner loop, and a force sensor 4 is used in the outer loop. Figure 7(a) shows observer 3
This is the experimental result when the observer 3 was not used, and (b) in the same figure is the experimental result when the observer 3 was used. As is clear from these experimental results, accurate force cannot be applied to the object with simple feedback from the force sensor 4 alone. However, when observer 3 was used, the force as instructed was applied.

FIGS. 8 to 10 are diagrams for explaining a second embodiment of the present invention.

In the case of this embodiment, the angular velocity ω is detected using the angular velocity meter 10, and the detection signal is given to the observer 11 (feedback means). The observer 11 has a simple structure including only one integrator 12, with the nominal value Dn of the viscous force of the mechanical system set to "0", and only the nominal values Ktn and Jn of the torque constant Kt and the moment of inertia J. The structure is designed with this in mind. Also, ω. means the cutoff frequency of the observer 11. The other configurations are the same as those of the first embodiment described above. As a result, the disturbance torque T, i-th 8
is determined by the following formula (2).

T, ++8-': ('I'ext + (,1-J
n) sω+Dω10 F →-(K t,,-K
t ) I a”J(ω, / (ω.+s))
......(2) In the front brace on the right side of the above equation, the first term is the load torque, the second term is the inertia force generated by fluctuations in the moment of inertia, and the third and fourth terms are the viscosity. The friction torque term due to force and Coulomb force, and the fifth term represent a torque ripple term due to fluctuations in the torque constant (for example, 4° torque ripple due to spatial harmonics of magnetic flux).

In the end, the disturbance torque Tldis to be fed back is expressed by the following equation (3).

'i' 111-” (K t o/K t )
(ω0/ωo+s) T dis...(3) As is clear from the above equation (3), the disturbance torque is set to a time constant of 1.
/ω. This means that the estimate is too late. here,
Angular acceleration is not directly expressed.

However, since the observer II having the configuration shown in FIG. 8 can be rewritten as shown in FIG. 9, the angular acceleration is determined as an implicit number. Further, FIG. 8 can also be equivalently transformed as shown in FIG. 1O. In the figure, the transfer characteristic that the disturbance imparts to the system is G (s). In other words, the cutoff frequency ω of the Habo observer. The following disturbances will be suppressed. This cutoff frequency ω. is 500 to 5 when using a normal brushless speed generator as a speed sensor.
000 (rad/5ec), and disturbance components below that value are suppressed.

Note that the control device of the present invention is not limited to being limited to a control device for an electric motor 1, but can be widely applied as a control device for various actuators. For example, in the case of a hydraulic actuator, the above-mentioned current Ia may be used as the operating amount of the hydraulic valve, and the torque constant of the hydraulic actuator proportional to the current Ia may be set as K.

[Effects] As explained above, the actuator control device of the present invention has a feedback shift configuration in which all disturbance torques that are not suppressed in the actuator control system are calculated at once, so that the actuator parameter values are By fixing it to a model with a nominal torque constant and a nominal moment of inertia even when the torque is fluctuating, it is possible to achieve a significant improvement in control performance.

[Brief explanation of the drawing]

1 to 7 are diagrams for explaining a first embodiment of the present invention, in which FIG. 1 is a block diagram of the entire control system, and FIG. 2 is a model of a converter driven by an electric motor. Figure 3 is a block diagram of the observer, Figures 4 and 5 are diagrams obtained by equivalently converting the block diagram of Figure 1, Figure 6 is a structural diagram of the experimental equipment, Figure 7 (a) is an explanatory diagram of the experimental results using the experimental apparatus shown in FIG. 6 without an observer, and FIG. 6(b) is an explanatory diagram of the experimental results using the experimental apparatus shown in FIG. 6 with the observer. 8 to 10 are diagrams for explaining the second embodiment of the present invention, in which FIG. 8 is a block diagram of the control system/σ body, and FIG. 9 and FIG. It is a diagram obtained by equivalently converting the block diagram of . FIG. 1I is a block diagram of a conventional servo motor control device u. 1...Electric motor, 2...Load, 3...
...Observer (feedback means).

Claims (1)

[Claims] An actuator whose force constant or torque constant is Kt and a load that applies a load force or load torque of T_e_x_t to the actuator are combined, and the inertia force calculated by replacing the center of gravity or the rotation axis The moment of inertia is J, the viscous friction force calculated by replacing the center of gravity or the viscous friction torque converted around the rotational axis is Dω, and the Coulomb friction force or Coulomb friction torque converted around the rotational axis by replacing the center of gravity is F. Sometimes, in an actuator control device that controls an output of the actuator according to a control amount Ia of the actuator, a velocity component ω or an acceleration component ωs of the actuator
From, the disturbance force or disturbance torque T_d given by the following formula
An actuator control device characterized by comprising feedback means for determining _i_a and feeding back a compensation control amount corresponding to this to the actuator. T_d_i_a=(T_e_x_t−T_e_x_t_
n)+(J-J_n)sω+(D-D_n)ω+(F-
F_n) + (Kt_n-Kt)Ia However, T_e_x_t_n is the nominal value of the load force or load torque, J_n is the nominal value of the inertia force or moment of inertia converted around the rotation axis based on the center of gravity substitution, and D is the nominal value of the inertia moment based on the center of gravity substitution. The viscosity coefficient or the viscosity coefficient when converted around the rotation axis, D_n is the viscosity coefficient when converted to the center of gravity or the nominal value of the viscosity coefficient when converted around the rotation axis, F_n is the Coulomb friction force when converted to the center of gravity or converted around the rotation axis. Kt_n is the nominal value of the force constant or torque constant of the actuator, and s is the Laplace operator.